<!DOCTYPE html>
<html lang="en" xmlns="http://www.w3.org/1999/html">
<head>
    <meta charset="UTF-8">
    <title>PPT效果</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        @-webkit-keyframes loops {

            0% {
                background: url(http://d.hiphotos.baidu.com/image/w%3D400/sign=c01e6adca964034f0fcdc3069fc27980/e824b899a9014c08e5e38ca4087b02087af4f4d3.jpg) no-repeat;
            }

            25% {
                background: url(http://b.hiphotos.baidu.com/image/w%3D400/sign=edee1572e9f81a4c2632edc9e72b6029/30adcbef76094b364d72bceba1cc7cd98c109dd0.jpg) no-repeat;
            }

            50% {
                background: url(http://b.hiphotos.baidu.com/image/w%3D400/sign=937dace2552c11dfded1be2353266255/d8f9d72a6059252d258e7605369b033b5bb5b912.jpg) no-repeat;
            }

            75% {
                background: url(http://g.hiphotos.baidu.com/image/w%3D400/sign=7d37500b8544ebf86d71653fe9f9d736/0df431adcbef76095d61f0972cdda3cc7cd99e4b.jpg) no-repeat;
            }

            100% {
                background: url(http://c.hiphotos.baidu.com/image/w%3D400/sign=cfb239ceb0fb43161a1f7b7a10a54642/3b87e950352ac65ce2e73f76f9f2b21192138ad1.jpg) no-repeat;
            }
        }

        .ani {

            width: 480px;
            height: 320px;
            margin: 50px auto;
            overflow: hidden;
            box-shadow: 0 0 5px rgba(0, 0, 0, 1);
            background-size: contain;
            background-position: center;
            -webkit-animation-name: loops;
            -webkit-animation-duration: 20s;
            -webkit-animation-iteration-count: infinite;
        }


    </style>
</head>
<body>
<div class="ani">

</div>
</body>
</html>
